Paris mayor Anne Hidalgo says Place de la Republique was sullied by people “looking for trouble” today. Violence quickly erupted between French riot police and a group of several hundred at a major square that was the site of a peaceful demonstration earlier. Climate demonstrators face riot police near the Place de la Republique after a planned climate march was canceled on the eve of the World Climate Change Conference 2015 (COP21) in Paris, France on Nov. 29, 2015.

The Paris police chief said that at least 100 people were detained after several hundred people, some masked and armed with projectiles, tried to force their way through a blockade at the Place de la Republique. The nearly two-week conference comes amid a state of emergency in France imposed after the Nov. 13 Paris attacks that bans marches.